FIGS. 13 and 14 show first and second prior art arrangements. In FIGS. 13 and 14, reference numeral 1 refers to a piezoelectric film, 2 to an insulator, 3 to a semiconductive epitaxial layer, 4 to a p-type or n-type semiconductor, 5 to an n-type or p-type semiconductor, 6 to an n.sup.+ -type or p.sup.+ -type semiconductor substrate, 7 to a gate electrode, 8 to a bottom electrode, 9 to a comb-shaped electrode, 10 to a bias source, 11 to an input terminal, and 12 to an output terminal.
The first prior art convolver (FIG. 13) is of a monolithic structure, which is manufactured easily and has quite a high convolution efficiency. Its details are given by the following document: